Fluoropolymers are a commercially useful and important class of materials. They can include fluoroplastics and cross-linked fluoroelastomers, such as copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomer, e.g., hexafluoropropylene. Many of these fluoropolymers are known to exhibit high thermal stability and usefulness at high temperatures. They are also known for their extreme toughness and flexibility at very low temperatures and are almost totally insoluble in a wide variety of organic solvents. Additionally, many fluoropolymers are resistant to many chemical compounds that might degrade other classes of less resistant materials and are further recognized for their barrier properties; i.e., their ability to prevent the passage of liquids or vapors.
Increased concerns with evaporative fuel standards have led to a need for improved fuel vapor barrier properties, such as in, for example, multi-layered fuel filler hoses and other multi-layered components of automobile emission control systems, to minimize the permeation of fuel vapors. These multi-layer products can include one or more fluorinated layers, which provide an inert, vapor barrier, and one or more other layers that can add strength, rigidity, or other mechanical properties to the multi-layered article.
These multi-layered articles should not delaminate during use. That is, the adhesive bond strength between the different layers of the multi-layered article should be sufficient to prevent the different layers from separating. A variety of methods have been employed with varying levels of success to increase the adhesive bond strength between fluoropolymer layers and non-fluorinated polymer layers, such as the use of adhesives, surface treatment of layers, and the use of “tie-layers”. However, there remains a need in the art for improved adhesion between fluoropolymer layers, particularly, between fluoroplastic and fluroelastomer layers. Without proper adhesion between these two layers, construction of multi-layered articles, such as fuel filler hoses, is not viable for production.
It would, therefore, be desirable to provide an adhesion promoter for bonding a fluoroplastic layer to a fluroelastomer layer in a multi-layered article, e.g., a fuel filler hose, such multi-layered article having a strong bond between these two layers and improved fuel vapor barrier layer properties.